Humoral and cellular immune responses in mice immunized with recombinant Mycobacterium bovis bacillus Calmette-Guerin producing a pertussis toxin-tetanus toxin hybrid protein

The development of combined vaccines constitutes one of the priorities in m odern vaccine research. One of the most successful combined vaccines in use is the diphtheria-pertussis-tetanus vaccine. However, concerns about the s afety of the pertussis arm have led to decreased acceptance of the vaccine but also to the development of new, safer, and effective acellular vaccines against pertussis. Unfortunately, the production cost of these new vaccine s is significantly higher than that of previous vaccines. Here, we explore the potential of live recombinant Mycobacterium bovis BCG producing the hyb rid protein S1-TTC, which contains the S1 subunit of pertussis toxin fused to fragment C of tetanus toxin, as an alternative to the acellular vaccines . S1-TTC was produced in two different expression systems. In the first sys tem its production was under the control of the 85A antigen promoter and si gnal peptide, and in the second system it was under the control of the hsp6 0 promoter. Although expression of the hybrid antigen was obtained in both cases, only the second expression system yielded a recombinant BCG strain a ble to induce both a specific humoral immune response and a specific cellul ar immune response. The antibodies generated were directed against the TTC part and neutralized toxin activity in an in vivo challenge model, whereas Interleukin-2 production was specific for both parts of the molecule. Since protection against tetanus is antibody mediated and protection against per tussis may be cell mediated, this constitutes a first promising step toward s the development of a cost-effective, protective, and safe combined vaccin e against pertussis, tetanus, and tuberculosis.